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  • 1
    ISSN: 1432-041X
    Keywords: Vitelline coat ; Oogenesis ; Differentiation ; Tunicates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have studied the differentiation of the vitelline coat (VC) of the ascidianCiona intestinalis. In the young previtellogenic oocyte the vitelline coat precursor material (VCPM) makes its first appearance as patches of fibrous material in close apposition to the outer surface of the oocyte. The presence of subcortical vescicles containing a fuzzy electron-dense material and their opening into the oocyte surface parallels the formation of VCPM. Numerous microvillar-like structures emerge from the oocyte surface. When the VCPM completely surrounds the oocyte the microvilli are withdrawn. An overall increase of VCPM parallels the growth of the oocyte. The next step in the differentiation of the vitelline coat consists in the packing of the constituent fibrils in a dense layer at its outer surface, i.e. the one in contact with the follicle cells. At this time the VC is penetrated by microvilli protruding both from the oocyte and follicle cells. The VC reaches its final structure and thickness at the time the test cells are extruded into the perivitelline space. The participation of the follicle cells in VC organization is also discussed.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 139 (1939), S. 536-555 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Vom, in der Orbitahöhle (nach Entfernung des Auges) oder unter der Haut autoplastisch transplantierten oberen Irisrand mit oder ohne Retina vonTriton oderDiscoglossus aus, regeneriert nie eine Linse. Transplantiert man dagegen das Irisstück in die Bauchhöhle, so bildet sich in einigen Fällen eine Linse. Das bringt zur Annahme, da\ in der Linsenregeneration aus einem isolierten Irisstück der Raum, der dem Stück in der Transplantationsstelle zur Verfügung steht, von höchster Wichtigkeit ist. Von Bedeutung ist auch die Retinaanwesenheit im transplantierten Stück, weil in allen Fällen, in denen man eine Linse erhalten hat, auch die Retina mittransplantiert worden war. Bei diesen Experimenten hat man in einigen Fällen auch Lentoiden erhalten. In den meisten Fällen der in der Orbita- oder Bauchhöhle transplantierten Stückchen regeneriert die Retina vom Irismaterial aus und sehr oft bildet das Stück kleine augenähnliche Kugeln. Die Retinaregeneration kommt entweder aus der „pars iridea retinae“ oder, ganz einfach, aus einer jeweiligen Irisstelle zustande durch Metaplasia der Iris- in Retinazellen. Die unter der Haut transplantierten Irisstückchen dagegen gehen fast immer zugrunde. Aus den in der Orbitahöhle transplantierten oder regenerierten Retinastückchen gehen fast immer Nervenfasern aus, die, durch das „Foramen opticum“ das Zwischenhirn erreichen. In den Transplantationen in der Bauchhöhle bemerkt man nie eine solche Nervenfasernbildung.
    Notes: Conclusioni Dal settore irideo superiore diTriton eDiscoglossus trapiantato autoplasticamente nell'orbita (dopo enucleazione del globo oculare) o sotto la cute, con o senza retina, non si forma mai una lente. Se invece l'innesto viene praticato nella cavità addominale allora, in una certa percentuale di casi, si ottiene una lente. CiÒ porta a pensare che nel determinismo del fenomeno una grande importanza debba essere attribuita allo spazio a disposizione del pezzo nella sede d'innesto. Molta importanza spetta anche alla presenza di retina ne l'innesto, giacchè i casi in cui si è avuta rigenerazione di lente appartengono tutti ad esperimenti di innesti di iride con retina. In questi esperimenti, in un certo numero di casi, si è anche avuta la formazione di lentoidi. Negli innesti nell'orbita e nell'addome quasi costante è la rigenerazione di retina dal materiale irideo innestato e niolto frequente la regolazione dell'innesto in forma di globetto oculo-simile. La rigenerazione della retina puÒ aver luogo o dalla pars iridea retinae o direttamente da qualsiasi punto dell'iride per diretta metaplasia delle cellule iridee in cellule retiniche. Negli innesti sotto cute invece il pezzo innestato va in genere incontro a disfacimento. Negli innesti nella cavità dell'orbita quasi costantemente si sono viste fibre nervose partirsi dalle masse retiniche e, attraverso alforo ottico, giungere fino al diencefalo. Negli innesti nella cavità addominale invece non si è mai vista tale neoformazione di fibre nervose.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 8 (1952), S. 29-30 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung Die Pigmentkörnchen aus dem Ei vonParacentrotus lividus bestehen aus einem Chromoproteid. Mit Erreichen des Blastulastadiums ist in den Körnchen auch Nukleinsäure enthalten.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Development genes and evolution 139 (1939), S. 78-85 
    ISSN: 1432-041X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung In 200 Tritonen verschiedenen Alters (Larven und Erwachsenen) wurden die Wachstumskorrelationen zwischen dem Augenbecher und der Linse untersucht. Es wurde klargelegt, daß das Wachstum der Linse viel schneller als dasjenige des Augenbechers vor sich geht, so daß bei den Erwachsenen die Linse 30mal größer ist als die der jüngsten Larven, der Augenbecher hingegen nur 9mal. Ein solcher Wachstumasinchronismus beeinflußt aber gar nicht die optischen Bedingungen des Auges, weil man in allen Entwicklungsstadien demonstrieren kann, daß der Brennpunkt der Linse immer auf die Retina fällt.
    Notes: Riassunto In 200 esemplari di varia età diTriton taen. edalp. si sono studiati i rapporti che nel corso dello sviluppo intercedono tra 1'accrescimento del calice ottico e quello della lente. Si è rilevato che la lente si accresce molto più rapidamente del calice ottico, sicché mentre nell'adulto la lente ha acquistato un volume 30 volte quello che aveva nelle più giovani larve esaminate, il volume del calice ottico è solo 9 volte quello iniziale. Questo asincronismo nell'accrescimento non influisce però sulle condizioni ottiche del sistema perché in tutti gli stadi di sviluppo si dimostra che il punto di convergenza di un fascio di raggi paralleli attraversanti la lente (il fuoco dèlia lente, cioe) e sempre situato nello spessore delia retina.
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 184 (1959), S. 68-69 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In this communication we wish to report the results of experiments indicating the presence of an inhibitor of the cytochrome oxidase activity in the unfertilized egg. Homogenates in sucrose or 0-01 M phosphate at p~H. 5-0 of unfertilized and fertilized jelly-free eggs of Paracentrotus lividus ...
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 188 (1960), S. 1195-1196 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We wish to report here some further experiments aimed mainly at obtaining the inhibitor in a purified form and at finding out about its chemical nature and its mode of action. Fig. 1 illustrates a typical experiment showing that the inhibitor (prepared as described by Maggio and Monroy1) ...
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 278 (1979), S. 165-166 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We can only speculate on the organisation of the cell membrane in the primitive prokaryotes; it may have been just a lipid bilayer. The major advance in this organisation must have been the insertion of proteins and/or glycoproteins in the bilayer. This step provided the cell membrane with an ...
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 4 (1981), S. 151-169 
    ISSN: 0148-7280
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Gamete Research 7 (1983), S. 85-102 
    ISSN: 0148-7280
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 6 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Philadelphia : Wiley-Blackwell
    Journal of Cellular and Comparative Physiology 30 (1947), S. 105-109 
    ISSN: 0095-9898
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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